In February, the British Parliament declared the colony of Massachusetts to be in open rebellion and authorized British troops to kill the violent rebels. They were ordered to destroy all of the stores that had ammunition, rifles, or other arms. Lt. Gen. Thomas Gage, the commander-in-chief of the British Army in America, was given command to quell the rebellion. He gave the orders to the British troops to destroy stores and rebels. He thought that the citizens were planning to collect enough arms to form a rebellion. Some American spies learned of the British orders and sent word to the townspeople of the local areas. Paul Revere and William Dawes were sent on different routes to warn the people about the British march to Concord. Before he left, Revere hung 2 laterns in the bell tower of the Old North Church, indicating that the British were coming by sea. Revere is noted as yelling the famous phrase "The Regulars are coming!" When they arrived in Lexington, Dr. Samuel Prescott joined Revere and Dawes in order to spread the word to the townspeople. Just after 1:00 A.M., between Lexington and Concord, Revere and Dawes ran into a British patrol. Revere was captured trying to escape and Dawes was forced away and rode back to Lexington. However, Prescott managed to finish his route to Concord.

On April 18, during the early morning hours, Gage dispatched troops under Lt. Col. Frances Smith and Maj. James Pitcairn to seize these munitions. The British force left Boston Common and landed their boats at Phip's Farm. Between 11:00 P.M. and 12:00 A.M., they waded ashore and waited for 2 hours while extra provisions were landed and distributed.

On April 19, between 1:00-2:00 A.M., Smith finally got his troops marching. When they arrived at Menotomy around 3:00 A.M., Smith learned that his advance was no longer a secret. He ordered Pitcairn ahead with 6 light companies to secure the bridges at Concord. The town of Lexington was a small crossroads community of 750 people. The British forces were prepared to face 500 militia. At first, there was about 170 militiamen that responded to the initial call to arms. After waiting for a while and not seeing any British forces, they were told to disperse and wait for the next call. At around 1:00 A.M., there were only 70 out of the original 170 militiamen that constituted the American force. Capt. John Parker managed to get about 40 militiamen to line up on the town's green. Another 30 or so militia were scattered around the Common grounds and the nearby buildings.

Around 4:30 A.M., Pitcairn neared the Lexington Common. Their guns were already primed and loaded. As the British approached Lexington, their advance guard captured 3 militia scouts that were just outside of the town, waiting to spot the British approach. The fourth militia scout, Thaddeus Brown, escaped capture and rode back into town. He warned Parker that the British were 1/2 mile away. Pitcairn was told that 500 militiamen were in town waiting for his force. He slowed his advance and waited for Smith's force to catch up to his.

Pitcairn ordered his men to surround the disarm the local militia that had gathered, specifically ordering them not to open fire on the militia. At nearly the same time, Parker ordered his militia to disperse, which they began to do. Pitcairn's plan was to not get bogged down, since his orders were to peacefully take possession of the Concord bridges. However, he could not leave the militia unmolested. Meanwhile, Parker was satisfied with the show of presence by the militia, and did not want to become engaged in a skirmish with the British.

At 5:00 A.M., just as the sun was beginning to rise, Pitcairn ordered his men to double their ranks, load their muskets, and sent them into the town at a double quick march. As the first British soldiers reached the community church at the southern end of the Common Green, Pitcairn rode to the front of his troops and ordered the militiamen to lay down their arms and disperse. Parker recognized that his 70 militiamen did not have a chance against the powerful British force and passed the word for his men to disperse. Parker told his men not to disarm but to just disperse. An unknown soldier accidently fired a shot. This was the infamous "Shot heard 'round the World." It was not known if it was the British or the militia that fired the shot.

The British soldiers immediately formed up in ranks fired on the militia, who were at a range of about 40 yards. Pitcairn moved among his soldiers, trying to regain order and telling his men to cease firing. The militia returned fire while they began to scatter for cover. Within a matter of minutes, the British troops made a bayonet charge and swept the militia from the Common Green. The British had broken ranks and were about to start breaking into houses when Smith arrived. Pitcairn and Smith soon got their troops under control and re-established order. They reformed their men into columns, fired a traditional victory volley, and headed on towards Concord. **See the Battle of Concord**

Pitcairn's horse was hit in two places. The regulars charged forward with bayonets. Captain Parker witnessed his cousin Jonas run through. Eight Massachusetts men were killed and ten were wounded against only one British soldier of the 10th Foot wounded (his name was Johnson, according to Ensign Jeremy Lister of that regt., present at this incident.) The eight British colonists killed, the first to die in the Revolutionary War, were John Brown, Samuel Hadley, Caleb Harrington, Jonathon Harrington, Robert Munroe, Isaac Muzzey, Asahel Porter, and Jonas Parker. Jonathon Harrington, fatally wounded by a British musket ball, managed to crawl back to his home, and he died upon his doorstep. One wounded man, Prince Estabrook, was a black slave who served in the town's militia.

The light infantry companies under Pitcairn at the common got beyond their officers' control. They were firing in different directions and preparing to enter private homes. Upon hearing the sounds of muskets, Colonel Smith rode forward from the grenadier column. He quickly found a drummer and ordered him to beat assembly. The grenadiers arrived shortly thereafter, and, once they were rounded up, the light infantry were then permitted to fire a victory volley, after which the column was reformed and marched towards Concord.